As a method for producing 7-octenal, a method in which 2,7-octadiene-1-ol is isomerized in the presence of a copper-based catalyst is known. It has been reported that 7-octenal can be selectively produced using, among copper-based catalysts, a copper-based catalyst precursor containing copper, iron, and aluminum (refer to PTL 1 to 3).
As a method for producing the copper-based catalyst precursor containing copper, iron, and aluminum, a method in which an aqueous solution of mixed metal salts including a water-soluble copper salt, a water-soluble iron salt, and a water-soluble aluminum salt as main components and a basic aqueous solution as a precipitant are reacted together so as to obtain a coprecipitate containing copper, iron, and aluminum, the coprecipitate is filtered, then, washed with water, dried, and calcined is known (refer to PTL 4 and 5).
When the coprecipitate containing copper, iron, and aluminum is calcined at a temperature in a range of 600° C. to 1,000° C., a spinel structure is formed. It is known that the atomic ratio between copper, iron, and aluminum in the coprecipitate is a factor that changes the dispersibility and the like of copper in the spinel structure, and furthermore, changes the activity and selectivity of the copper-based catalyst (refer to PTL 4 to 8).
It is also known that, in a case in which a copper-based catalyst precursor containing copper, iron, and aluminum which is obtained by coprecipitating a copper compound, an iron compound, and an aluminum compound on the surface of a carrier, and calcining the coprecipitate at 750° C. is used in a hydrogenation reaction, the activity and selectivity of the copper-based catalyst are changed depending on the kind of the carrier (PTL 9). That is, it is known that the atomic ratio between copper, iron, and aluminum in the coprecipitate, the kind and content of the carrier included in the coprecipitate, and the calcination temperature for turning the coprecipitate into the copper-based catalyst precursor change the activity and selectivity of the copper-based catalyst.
When the coprecipitate containing copper, iron, and aluminum is dried at a temperature in a range of 100° C. to 150° C., and then calcined at a temperature in a range of 600° C. to 1,000° C., a copper-based catalyst precursor can be obtained. Furthermore, when the copper-based catalyst precursor is hydrogen-reduced, the precursor becomes activated, and then can be used in desired reactions as a copper-based catalyst. Alternatively, it is also possible to crush the precursor after the calcination, activate the obtained powder-form copper-based catalyst precursor through hydrogen reduction, and use the powder in reactions as a powder-form copper-based catalyst. When it is also possible to use the calcined powder-form copper-based catalyst precursor formed through compression, extrusion, or the like as desired, it is also possible to use the dried coprecipitate that is formed through compression, extrusion, or the like, and then is calcined (refer to PTL 5, 12, and the like).
It is known that the copper-based catalyst precursor containing copper, iron, and aluminum can be used in a variety of hydrogenation reactions such as hydrogenation from an aliphatic ester compound to a higher alcohol (refer to PTL 4 to 12).